<h2>多选题</h2>
<ul class="chooseUl">
    <li>
        <h3>{{item.question}}</h3>
        <div class="checkDiv">
            <label nz-checkbox [ngModel]="userExam.answer1" (ngModelChange)="customChange($event, 1)">
                <span>{{item.optionA}}</span>
            </label>
            <label nz-checkbox [ngModel]="userExam.answer2" (ngModelChange)="customChange($event, 2)">
                <span>{{item.optionB}}</span>
            </label>
            <label nz-checkbox [ngModel]="userExam.answer3" (ngModelChange)="customChange($event, 3)">
                <span>{{item.optionC}}</span>
            </label>
            <label nz-checkbox [ngModel]="userExam.answer4" (ngModelChange)="customChange($event, 4)">
                <span>{{item.optionD}}</span>
            </label>
        </div>
    </li>
</ul>